An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The observation and recording of large extents of the sky with a particular instrument using one or more wavelengths in the same spectral domain. → survey.

→ sky; → survey.

The illumination of the night sky in urban areas caused by wasted light shining upward scattered off dust, humidity, and air. Skyglow is a type of → light pollution that results from light fixtures emitting a portion of their light directly upward into the sky. Light scattered in the atmosphere creates an orange-yellow glow above a city or town. Skyglow interferes with sensitive astronomical instruments designed to capture light from distant stars, nebulae, and galaxies. Skyglow can often be detected hundreds of kilometers away.

→ sky; → glow.

Nur, → light; foruq, → glow; šahr, → city; âsmân, → sky.

Solar radiation which reaches the observer from the general sky. It is sunlight which has undergone multiple scattering events with the molecules of the Earth's atmosphere (Rayleigh scattering) or with clouds or other aerosols in the atmosphere. High levels of skylight reduce the contrast of a shadow. Also known as diffuse skylight, diffuse sky radiation.

→ sky; → light.

A broad, flat, somewhat thick piece of stone, wood, or other solid material (Dictionary.com).

M.E sclabbe, slabbe of unknown origin, maybe related to O.Fr. escopel, escalpe "thin fragment of wood."

Tiyât, from Kurd. (Ilâm) teyat "slab."

An oblique line (/) used between alternatives (e.g. and/or), in fractions (e.g. 4/5), or in percent ratios (e.g. kilometer/hour).

From M.E. slaschen, perhaps from M.Fr. esclachier "to break," variant of esclater "to break, splinter."

Eslaš, loan from E.

A fine-grained rock formed by the metamorphosis of clay, shale, etc., that tends to split along parallel cleavage planes, usually at an angle to the planes of stratification (Dictionary.com).

M.E. sclate, from M.Fr. esclate, feminine of esclat "piece split off," (Fr. éclat) so called because the rock splits easily into thin plates.

Palmé "slate," "a board on which children learn to read," ultimately from Proto-Ir. *parn-, *parm- "feather," PIE *pernom-, *pornos- "feather," → tablet.

Precipitation in the form of → transparent or → translucent ice → pellets that are 5 mm or less in diameter, created by the freezing of rain as it falls (distinguished from hail).

M.E. slete; akin to M.H.G. sloz, M.L.G. sloten (plural) "hail."

Tangar, from Gilaki tangar "fine hail."

In → supersymmetry theories, a hypothetical → boson super-partner of a → lepton. See also → squark

s from → supersymmetry; → lepton.

The action of rapidly moving a telescope in the alpha or delta direction under computer control as it moves to point at a new position in the sky.

Slew "to turn, swing, twist," earlier slue a nautical word, of unknown origin.

Tondrâneš, literally "driving fast," from tond "swift, rapid, brisk; fierce, severe" (Mid.Pers. tund "sharp, violent;" Sogdian tund "violent;" cf. Skt. tod- "to thrust, give a push," tudáti "he thrusts;" L. tundere "to thrust, to hit" (Fr. percer, E. pierce, ultimately from L. pertusus, from p.p. of pertundere "to thrust or bore through," from per- + tundere, as explained); PIE base *(s)teud- "to thrust, to beat") + râneš, verbal noun of rândan "to push, drive, cause to go," causative of raftan "to go, walk, proceed" (present tense stem row-, Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack").

A motor designed to drive a high-speed radar antenna for slewing to monitor a target.

→ slewing; → drive

1) A thin, broad piece cut from something.
2) To cut into slices; divide into parts (Dictionary.com).

O.Fr. escliz "splinter, fragment" (Fr. éclisse), a back-formation from esclicier "to splinter, shatter, smash;" cf. O.H.G. slihhan.

Qâc, contraction of qârc, from karj "slice, a slice of melon; a piece cut out of the collar of a garment;" ultimately from Proto-Ir. *kartaka-, from *kart- "to cut," cf. Av. karət- "to cut;" Skt. kart- "to cut," karəta- "knife;" Mid.Pers. kârt, → knife.

An important astronautical technique whereby a spacecraft takes up a tiny fraction of the gravitational energy of a planet it is flying by, allowing it to change trajectory and speed. Also known as → gravitational slingshot or → gravitational assist.

Slingshot, from sling, from M.E. slyngen, from O.N. slyngva "to sling, fling" + shot, from M.E., from O.E. sc(e)ot, (ge)sceot; cf. Ger. Schoss, Geschoss; → effect.

Oskar, → effect; falâxan "sling;" from Av. fradaxšana- "sling," fradaxšanya- "sling, sling-stone;"

A long, thin opening in a spectrograph allowing only the light studied to fall on the prism.

O.E. slitan "to cut or tear up, slit;" cf. O.S. slitan, O.N. slita, M.L.G., M.Du. sliten, Du. slijten, O.H.G. slizan, Ger. schleißen "to slit."

Šekâf "slit," from Mod./Mid.Pers. škâf- škâftan "to split, burst;" Proto-Iranian *kap-, *kaf- "to split;" cf. Gk. skaptein "to dig;" L. cabere "to scratch, scrape," P.Gmc. *skabanan (Goth. skaban; Ger. schaben; E. shave). PIE base *(s)kep- "to cut, to scrape, to hack."

A type of spectrograph that uses a slit to provide resolution.

→ slit; → spectrograp.

The width size of the slit which determines the spectral resolution of a spectrograph.

→ slit; → width.

A major → redshift survey using a dedicated 2.5-m wide angle telescope with different modes in → imaging and → spectroscopy. The telescope, a modified → Ritchey-Chretien→ altitude-azimuth type is located at Apache Point Observatory, south east New Mexico, United States. A large consortium of universities and institutions all over the world participate in the project. The telescope started its observations in 2000, taking spectra and images of about 35% of the night sky, with 3 million spectra and 500 million images coming together to form the most comprehensive astrophysical catalog in the world. This catalog contains millions of galaxies up to z = 1, bright → quasars up to z = 6, with images in five major filter bands (u, g, r, i and z). SDSS was divided into multiple surveys/projects: SDSS I (2000-2005); SDSS II (2005-2008), including the Sloan Supernova Survey; SDSS III (2008-2014), including the APO Galactic Evolution Experiment (APOGEE), Baryon Oscillation Spectroscopic Survey (BOSS); SDSS IV (2014-2020), including the Mapping Nearby Galaxies at APO (MaNGA).

Named after the Alfred P. Sloan Foundation, which contributed significant funding; → digital; → sky; → survey.

1) An inclined surface; deviation from the horizontal or vertical.
2) The tangent of the angle formed by the intersection of a given straight line and the X-axis of a system of Cartesian coordinates.
3) The derivative of the function whose graph is a given curve evaluated at a designated point.
4) The exponent of the → initial mass function . See also → Salpeter slope.
5) → slope parameter.

From M.E. aslope (adv.) "on the incline," from O.E. *aslopen, p.p. of aslupan "to slip away," from a- "away" + slupan "to slip."

Šib "slope, descent, declivity," contraction of nešib, našib "declivity, descent; lowness of ground, slope of any place;" Mid.Pers. nišēp "declivity, (astrology) dejection," Av. *nixšvaēpā-, xšvaēpā- "bottom, rear."

In a → power-law distribution or → regression, the → exponent that represents the effect of the → independent variable, x, on the → dependent variable, y. X has no association with y if the slope parameter = 0 and x has strong association with y if the slope parameter is large.

→ slope; → parameter.

Moving or proceeding with little or less than usual speed or velocity.

O.E. slaw "inactive, sluggish;" cf. O.S. sleu "blunt, dull," M.Du. slee, Du. sleeuw "sour, blunt," O.H.G. sleo "blunt, dull," O.N. sljor, Dan. sløv, Swed. slö "blunt, dull."

Âhesté "slow, quiet, tender, soft," ultimately from Proto-Iranian *ā-hasta-ka-, literally "at rest, motionless, seated." The first and third components are affixes, the main component from *had- "to "sit, be seated;" cf. Av. had- "to sit" (nī...hazdiiāt "would sit down"); Pers. nešastan "to sit;" PIE base *sed- "to sit;" cf. Skt. sad- to sit," sidati "sits;" Gk. hezomai "to sit," hedra "seat, chair;" L. sedere "to sit;" O.Ir. suide "seat, sitting;" Welsh sedd "seat;" Lith. sedmi "to sit;" Rus. sad "garden;" Goth. sitan, Ger. sitzen; E. sit.

A neutron whose kinetic energy does not exceed about 10 electron-volts. Also called → thermal neutron.

→ slow; → neutron.